Manufacturing method and apparatus of phase shift mask blank

ABSTRACT

There is disclosed a manufacturing method of a phase shift mask blank in which dispersions of phase angle and transmittance among blanks can be reduced as much as possible and yield is satisfactory. In the manufacturing method of the phase shift mask blank, a process of using a sputtering method to continuously form a thin film on a transparent substrate comprises: successively subjecting a plurality of substrates to a series of process of supplying the transparent substrate into a sputtering chamber, forming the thin film for forming a pattern in the sputtering chamber, and discharging the transparent substrate with the film formed thereon from the sputtering chamber; supplying and discharging the transparent substrate substantially at a constant interval; and setting a film formation time to be constant among a plurality of blanks.

This application claims the Paris convention priority of Japanese patentapplication 2000-277354 filed on Sep. 12, 2000, the entire disclosure ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

i) Field of the Invention

The present invention relates to a manufacturing method and apparatus ofa phase shift mask blank which is suitable particularly for ArF or F₂excimer laser.

ii) Description of the Related Art

In recent years, it has been clarified that high resolution and focusdepth are two important properties required for photolithography but arein a contradictory relation with each other, and that a practicalresolution cannot be enhanced only by high NA and short wavelength of alens of an exposure apparatus (Monthly Semiconductor World 1990.12,Applied Physics Vol. 60, November, 1991, and the like).

Under such situation, phase shift lithography has been noted as thenext-generation photolithography technique, and partially brought topractical use. The phase shift lithography is a method for enhancing theresolution of photolithography by change only of a mask without changingan optical system. When a phase difference is applied between exposurelights transmitted through the photo mask, mutual interference of thetransmitted lights can be utilized to rapidly enhance the resolution.

The phase shift mask is a mask for using light strength informationtogether with phase information. Various types of the masks are knownsuch as Levenson type, auxiliary pattern type, and self-matching type(edge emphasizing type). These phase shift masks have a complicatedconstitution and requires a high degree of manufacturing technique ascompared with the conventional photo mask which has only the lightstrength information.

In recent years, a so-called halftone type phase shift mask has beendeveloped as one of the phase shift masks.

In the halftone phase shift mask, a light semi-transmission section hastwo functions: a shield function of substantially shielding the exposurelight; and a phase shift function of shifting (usually reversing) alight phase. Therefore, it is unnecessary to separately form a shieldfilm pattern and phase shift film pattern. This type of phase shift maskis simple in constitution and easy in manufacturing.

In the halftone phase shift mask, a mask pattern is processed by a dryetching process. However, in a method of realizing the shield functionand phase shift function by separate layers, a high degree of control isnecessary for both the layer having the shield function and the layerhaving the phase shift function in order to obtain a satisfactorypattern shape. On the other hand, when a single-layer lightsemi-transmission portion having both the shield function and the phaseshift function is constituted, a single etching process can be used.Therefore, a manufacturing process of the mask can be simplified, and asatisfactory pattern shape can easily be obtained.

For the halftone phase shift mask, as shown in FIG. 10, a mask patternformed on a transparent substrate 100 is constituted of a lighttransmission portion (transparent substrate exposed portion) 200 fortransmitting a light which is strong enough to substantially contributeto exposure, and a light semi-transmission portion (shield and phaseshifter portion) 300 for transmitting a light which is not strong enoughto substantially contribute to the exposure (FIG. 10A). Additionally,the phase of the light transmitted to the light semi-transmissionportion is shifted, and the light semi-transmission portion is broughtto a substantially reversed relation with respect to the phase of thelight transmitted through the light transmission portion (FIG. 10B). Thelights transmitted in the vicinity of a boundary between the lightsemi-transmission portion and the light transmission portion and turnedto the opposite portions by diffraction phenomenon cancel each other.Thereby, light strength in the boundary is substantially set to zero,and contrast, that is, resolution of the boundary is enhanced (FIG.10C).

Additionally, the light semi-transmission portion or film (phase shiftlayer) in the halftone phase shift mask or blank needs to indicate arequired optimum value with respect to both transmittance and phaseshift amount. Concretely, (1) the transmittance in exposure wavelengthof i-ray, KrF excimer laser, ArF excimer laser, or the like can beadjusted in a range of 3 to 20%, (2) a phase angle can be adjustedusually to a value in the vicinity of 180° in the exposure wavelength,and (3) the transmittance needs to be usually testable in a range of 65%or less in test wavelengths such as 257 nm, 266 nm, 364 nm, and 488 nm.

However, with shortening of the wavelength of laser for use in exposureto ArF excimer laser (193 nm) from i-ray (365 nm) and KrF excimer laser(248 nm), the following problem is generated in the conventionalhalftone phase shift mask and the manufacturing method of the mask.

That is, in mass production of the phase shift mask blanks, when thereare dispersions of the phase angle and transmittance among the blanks orin the plane, yield is bad. Particularly in the mask blanks for theshort wavelength of ArF or F₂ excimer laser, the dispersions of thephase angle and transmittance among the blanks and in the plane in theconventional mask blanks for i-ray and KrF excimer laser are large, andthe yield is bad. Therefore, the mask blanks cannot be applied as theyare.

SUMMARY OF THE INVENTION

The present invention has been developed under the aforementionedbackground, and a first object thereof is to provide a manufacturingmethod of a phase shift mask blank in which dispersions of a phase angleand transmittance among blanks can be reduced as much as possible and ayield is satisfactory.

Moreover, a second object is to provide a manufacturing method of thephase shift mask blank in which the dispersions of the phase angle andtransmittance in a plane of the blanks can be reduced as much aspossible and the yield is satisfactory.

Furthermore, a third object is to provide a manufacturing apparatus ofthe phase shift mask blank in which the dispersions of the phase angleand transmittance among the blanks can be reduced as much as possibleand which can be manufactured with a satisfactory yield.

Additionally, a fourth object is to provide a manufacturing apparatus ofthe phase shift mask blank in which the dispersions of the phase angleand transmittance in the plane of the blanks can be reduced as much aspossible and which can be manufactured with the satisfactory yield.

To achieve the aforementioned objects, the present invention has thefollowing constitutions.

(Constitution 1) A method of continuously manufacturing a plurality ofphase shift mask blanks each having at least a phase shift film on atransparent substrate, the method comprising a step of:

using a sputtering method to continuously form the phase shift film onthe transparent substrate,

wherein a dispersion of a phase angle of the phase shift film among theplurality of blanks is within ±2°.

(Constitution 2) A method of continuously manufacturing a plurality ofhalftone phase shift mask blanks each having at least a lightsemi-transmission film on a transparent substrate, the method comprisinga step of:

using a sputtering method to continuously form the lightsemi-transmission film on the transparent substrate,

wherein dispersions of a phase angle and a transmittance of the lightsemi-transmission film among the plurality of halftone phase shift maskblanks are within ±2° and within ±4%, respectively.

(Constitution 3) A method of continuously manufacturing a plurality ofphoto mask blanks each having at least a thin film for forming a patternon a transparent substrate, the method comprising a step of:

using a sputtering method to continuously form the thin film on thetransparent substrate,

wherein the step of using the sputtering method to continuously form thethin film on the transparent substrate comprises steps of: successivelysubjecting a plurality of substrates to a series of processes ofsupplying the transparent substrate into a sputtering chamber, formingthe thin film for forming the pattern in the sputtering chamber, anddischarging the transparent substrate with the film formed thereon fromthe sputtering chamber; and supplying and discharging the transparentsubstrate substantially at a constant interval in order to set a filmformation time to be constant among the plurality of blanks, and

at least first to fifth photo mask blanks after start of film formationare excluded from the photo mask blanks obtained in the step.

(Constitution 4) The manufacturing method according to constitution 3wherein the thin film for forming the pattern is a phase shift film, andthe photo mask blank is a phase shift mask blank.

(Constitution 5) The manufacturing method according to constitution 3wherein the thin film for forming the pattern is a lightsemi-transmission phase shift film, and the photo mask blank is ahalftone phase shift mask blank.

(Constitution 6) A manufacturing method of a photo mask blank having athin film for forming at least a pattern on a transparent substrate, themethod comprising steps of:

rotating the substrate; sputtering a target disposed opposite to aposition whose center axis deviates from a center axis of the substrate;and forming the thin film.

(Constitution 7) The manufacturing method according to constitution 6wherein the target and the substrate are disposed so that oppositesurfaces of the substrate and target form a predetermined angletherebetween.

(Constitution 8) The manufacturing method according to constitution 6 or7 wherein the step of forming the film comprises a step of rotating thetransparent substrate integer times between start of film formation andend of the film formation.

(Constitution 9) The manufacturing method according to any one ofconstitutions 6 to 8 wherein the thin film for forming the pattern is aphase shift film, and the photo mask blank is a phase shift mask blank.

(Constitution 10) The manufacturing method according to constitution 9wherein a dispersion of a phase angle of the phase shift film in a planeis within ±2°.

(Constitution 11) The manufacturing method according to any one ofconstitutions 6 to 10 wherein the thin film for forming the pattern is alight semi-transmission phase shift film, and the photo mask blank is ahalftone phase shift mask blank.

(Constitution 12) The manufacturing method according to constitution 11wherein a dispersion of a phase angle of the light semi-transmissionphase shift film in a plane is within ±2° and a dispersion of atransmittance in the plane is within ±4%.

(Constitution 13) The manufacturing method according to constitution 11or 12 wherein the light semi-transmission phase shift film is formed bysputtering the target formed of a metal and silicon in an atmospherecontaining nitrogen, contains the metal, silicon and nitrogen as mainconstituting components, and is formed so that a content of nitrogen inthe light semi-transmission phase shift film is larger than a content ofsilicon.

(Constitution 14) A photo mask manufactured by patterning the thin filmin the photo mask blank according to any one of constitutions 1 to 13.

(Constitution 15) A pattern transfer method of using the photo maskaccording to constitution 14 to transfer a pattern.

(Constitution 16) A manufacturing apparatus of a photo mask blank,comprising at least: a load lock mechanism for introducing substratesone by one; a substrate conveying mechanism for introducing thesubstrates one by one to a sputtering chamber from a load lock chamberat a constant interval; the sputtering chamber for forming a film on thesubstrate; and an unload lock mechanism for discharging the substratesone by one from the sputtering chamber.

(Constitution 17) A manufacturing apparatus of a photo mask blank,comprising: a substrate laying base having a rotation mechanism; and atarget disposed opposite to a position whose center axis deviates from acenter axis of a substrate.

(Constitution 18) The manufacturing apparatus according to constitution17 wherein the target and the substrate are disposed so that oppositesurfaces of the substrate and target form a predetermined angletherebetween.

(Constitution 19) The manufacturing apparatus of the halftone phaseshift mask blank according to any one of constitutions 16 to 18,comprising: means for detecting a rotation position of the substrate;and means for turning OFF electric discharge (ending film formation)when the substrate rotated integer times after turning ON the electricdischarge (starting the film formation) is allowed to reach the samerotation angle position as a rotation angle position for turning ON theelectric discharge.

According to the constitutions 1 and 2, the dispersion of the phaseangle of the phase shift film among the phase shift mask blanks iswithin ±2°, or the dispersions of the phase angle and transmittance ofthe light semi-transmission film among the halftone phase shift maskblanks are within ±2° and within ±4%, respectively. Therefore, the phaseshift mask for a short wavelength of ArF or F₂ excimer laser can bemanufactured in a mass and can practically be used. When this range isexceeded, it is difficult to mass-manufacture and practically use thephase shift mask for the short wavelength of ArF or F₂ excimer laser.

Additionally, even in the present situation, the masks for KrF excimerlaser can practically be used. However, smaller dispersions of the phaseangle and transmittance of the light semi-transmission film among themask blanks are preferable. Therefore, the invention according to theconstitutions 1 and 2 can also be applied to the phase shift mask blankfor the KrF excimer laser.

According to the constitutions 3 to 5, the dispersions of filmproperties (transmittance (OD), film thickness, and the like) in thephoto mask blank among the blanks can be suppressed. It is particularlypossible to realize the manufacturing of the phase shift mask in whichthe dispersion of the phase angle of the phase shift film among thephase shift mask blanks is within ±2°, or the dispersions of the phaseangle and transmittance of the light semi-transmission film among thehalftone phase shift mask blanks are within ±2° and within ±4%,respectively.

According to the constitutions 6 to 12, the dispersions of the filmproperties (transmittance (OD), film thickness, and the like) in theplane in the photo mask blank can be suppressed. It is particularlypossible to realize the phase shift mask blank in which the dispersionof the phase angle of the phase shift film in the plane of the phaseshift mask blank is within ±2°, or the dispersions of the phase angleand transmittance of the light semi-transmission film in the plane ofthe halftone phase shift mask blank are within ±2° and within ±4%,respectively. Therefore, the phase shift mask for the short wavelengthof the ArF or F₂ excimer laser can be brought to practical use. Whenthis range is exceeded, it is difficult to practically use the phaseshift mask for the short wavelength of the ArF or F₂ excimer laser.

Additionally, even in the present situation, the mask for the KrFexcimer laser can practically be used. However, smaller dispersions ofthe phase angle and transmittance of the light semi-transmission film inthe plane of the mask blank are preferable. Therefore, the inventionaccording to the constitutions 6 and 12 can also be applied to the phaseshift mask blank for the KrF excimer laser.

According to the constitution 13, the dispersion of the phase angle canfurther be suppressed.

According to the constitution 14, it is possible to obtain the photomask in which the dispersion among the masks or in the mask plane issuppressed.

According to the constitution 15, a superior fine pattern processing canbe realized.

According to the apparatus of the constitutions 16 to 19, thedispersions of the film properties (transmittance (OD), film thickness,and the like) in the photo mask blank among the blanks or in the planecan be suppressed. It is particularly possible to realize themanufacturing of the phase shift mask blank in which the dispersion ofthe phase angle of the phase shift film among the phase shift maskblanks or in the plane is within ±2°, or the dispersions of the phaseangle and transmittance of the light semi-transmission film among thehalftone phase shift mask blanks or in the plane are within ±2° andwithin ±4%, respectively.

The present invention will be described hereinafter in more detail.

As a result of pursuing of researches in order to achieve theaforementioned objects, the following has been obtained.

In the halftone phase shift mask, it is functionally important to adjustthe phase angle and transmittance of the light semi-transmission portionand obtain desired values. For an error range of the phase angle andtransmittance, fluctuation among blanks (dispersion among blanks), andin-blank distribution (in-plane dispersion) require to be about ±2°, and±4°, respectively. Examples of a factor which changes the phase angleand transmittance include: (1) film formation procedure of the lightsemi-transmission film; (2) property of a sputtering apparatus forforming the light semi-transmission film, and (3) material of the lightsemi-transmission film.

(1) The film formation procedure for forming the light semi-transmissionfilm will be described in detail.

To determine a film formation time of the light semi-transmission filmat the start and end of sputtering, when an interval between thesputtering end and the next sputtering start is set to be constant, thefluctuations of the phase angle and transmittance among blanks(dispersion among blanks) are effectively within ±2°, and within ±4°(reproducibility is effectively enhanced). In sputtering phenomenon,temperature and surface state of a target or a shield are changed, and adegree of vacuum in a vacuum tank is also changed. In a conventionalintermittent sputtering in which the interval between the sputtering endand the next sputtering start is not constant, the state of the targetor the shield changes every moment. However, in the present invention,when the interval between the sputtering end and the next sputteringstart, and sputtering time and condition are always set to be constant,the fluctuations of the phase angle and transmittance are reduced on andafter forming five to ten blanks. That is, when the lightsemi-transmission film is continuously formed at a constant interval,and fifth to tenth blanks formed after the start are excluded, it ispossible to steadily manufacture the halftone phase shift mask blankshaving less fluctuations of the phase angle and transmittance.Concretely, it is possible to steadily manufacture the halftone phaseshift mask blanks in which the dispersions of the phase angle andtransmittance among the blanks are within ±2°, and within ±4°,respectively.

In order to realize this process, as shown in FIG. 1, a load lockmechanism needs to be disposed which can constantly hold a sputteringvacuum tank (sputtering chamber) in a high vacuum state. In thisapparatus constitution, introduction of the substrate to the sputteringchamber from a load lock chamber is continuously performed at a constantinterval. For this, the load lock mechanism for introducing thesubstrates one by one needs to be disposed. Additionally, a capacity ofthe load lock chamber needs to be designed such that the substrate iscontinuously introduced to the sputtering chamber from the load lockchamber at the constant interval.

In the conventional manufacturing apparatus of the halftone phase shiftmask blanks, about ten substrates are set in the load lock chamber froma viewpoint of throughput. In this system (or an in-line system), sincethe capacity of the load lock chamber is large, much time is requiredfor setting the inside of the load lock chamber at a predetermineddegree of vacuum, and film formation is not performed in the sputteringchamber during this time. Therefore, when the film formation all endsand the next cassette is set in the load lock chamber in order toperform the film formation, the substrate is not continuously suppliedto the sputtering chamber at the constant interval. In this case, whenthe substrate is not continuously introduced to the sputtering chamberat the constant interval, the film formation in the sputtering chamberis not stabilized, the dispersions of the phase angle and transmittanceamong the blanks are large in the first five to ten blanks, and yield isdisadvantageously bad.

In FIG. 1, a valve 12 for separating a load lock chamber 11 from theatmosphere, and a valve 14 for separating the load lock chamber 11 froma sputtering chamber 13 are attached to the load lock chamber 11. Theload lock chamber 11 has a sheets system in which the substrate cancontinuously be introduced to the sputtering chamber at the constantinterval as described above. The load lock chamber is also designed tohave a predetermined capacity. The sputtering chamber 13 has a functionequivalent to a function of the vacuum tank in which sputtering isperformed as described later and shown in FIG. 2. When the substrate isintroduced to the sputtering chamber 13 by a robot arm, a conveyingchamber 15 may be disposed between the sputtering chamber 13 and theload lock chamber 11. For a robot arm 19, when an arm 19 a opens/closesin a direction A, a hand 19 b can move in a direction B. Moreover, therobot arm 19 can rotate in a direction C. The robot arm 19 is alsoconstituted to be movable in a vertical direction with respect to asheet surface. Furthermore, in order to enhance throughput of filmformation, an unload lock chamber 16 having a constitution similar tothat of the load lock chamber 11 may be added. An example of the processfor forming the light semi-transmission film on the transparentsubstrate will be described with reference to FIG. 1.

1) After the valve 14 is closed, the inside of the load lock chamber 11is set to be in an atmospheric pressure through venting.

2) The valve 12 is opened and one transparent substrate is introducedinto the load lock chamber 11.

3) The valve 12 is closed and the load lock chamber 11 is evacuated.

4) After the load lock chamber 11 reaches a predetermined degree ofvacuum, the valve 14 is opened and the transparent substrate is moved tothe sputtering chamber 13.

5) A constitution described later and shown in FIG. 2 is used to formthe light semi-transmission film in the sputtering chamber 13.

6) After the end of formation of the light semi-transmission film, avalve 17 is opened and the substrate is moved to the unload lock chamber16. In this case, it is necessary to evacuate the unload lock chamber 16to the predetermined degree of vacuum.

7) After the valve 17 is closed, the unload lock chamber is brought tothe atmospheric pressure through venting.

8) A valve 18 is opened and the substrate is removed.

From when the light semi-transmission film is formed in the sputteringchamber 13, until the substrate is moved to the unload lock chamber 16from the sputtering chamber 13, steps 1) to 4) are ended, and the nextsubstrate is allowed to be on standby in the load lock chamber 11. Whenthe previous film formation ends, and the substrate is moved to theunload lock chamber 16 from the sputtering chamber 13, the transparentsubstrate having been on standby is moved to the sputtering chamber 13,and the light semi-transmission film is successively formed. By thisprocess, it is possible to successively (continuously) form the lightsemi-transmission film at the constant interval excluding a time ofmaintenance of the apparatus.

(2) The property of the sputtering apparatus for forming the lightsemi-transmission film will next be described in detail. Since a gaspressure during the sputtering for forming the light semi-transmissionfilm, output of a sputtering DC power supply, and a sputtering timedirectly influence the transmittance and phase angle, precision of a gasflow rate controller, DC power supply or another apparatus needs to beenhanced. It is also necessary to enhance the precision of a set signalemitted from the controller. Since the gas pressure during thesputtering is also influenced by exhaust conductance of the apparatus, amechanism able to accurately determine an open degree of an exhaust portvalve and a position of the shield is also necessary. A concrete controlprecision will be described later.

Moreover, for a film containing silicon nitride, moisture generated froman inner wall of the vacuum tank, or another gas largely influences anoptical property of the film. It is therefore necessary to dispose apump which can sufficiently evacuate the vacuum tank, and a mechanismwhich can bake the inner wall of the vacuum tank. The degree of vacuumin the vacuum tank needs to be about 2×10⁻⁵ pa or less at a filmformation speed of 10 nm/min, and 1×10⁻⁵ pa or less at a film formationspeed of 5 nm/min.

Furthermore, in order to suppress the distributions of the phase angleand transmittance in the blanks (dispersions in the plane) within ±2°and ±4°, the transparent substrate needs to be rotated during the filmformation. It is further necessary to rotate the transparent substrateinteger times between the start and the end of the film formation whilethe film formation is performed. To this end, for example, the rotationangle position of the substrate of a time at which electric discharge isturned ON (start of film formation) is detected by a sensor fordetecting the rotation angle position of the substrate. Furthermore, bythis sensor, when the substrate rotates integer times and reaches thesame rotation angle position as that of the ON time of the electricdischarge, the electric discharge is turned OFF (film formation isended). This mechanism needs to be disposed.

The distributions of the phase angle and transmittance in the plane alsochange with a positional relation between the substrate and the target.The positional relation between the target and the substrate will bedescribed with reference to FIG. 8.

An offset distance (distance between a center axis of the substrate anda straight line passed through a center of the target and extended inparallel to the center axis of the substrate) is adjusted by an area inwhich the distributions of the phase angle and transmittance are to besecured. Generally in a large area in which the distributions are to besecured, a necessary offset distance is large. In order to realize thephase angle distribution within ±2° and transmittance distributionwithin ±4° in a 152 mm square substrate as in the present embodiment,the offset distance needs to be in a range of about 200 mm to 350 mm,and a preferable offset distance is in a range of 240 mm to 280 mm.

An optimum range of a vertical distance between the target and thesubstrate (T/S) changes with the offset distance. However, in order torealize the phase angle distribution within ±2° and transmittancedistribution within ±4° in the 152 mm square substrate, the verticaldistance between the target and the substrate (T/S) needs to be about200 mm to 380 mm, and preferable T/S is in a range of 210 mm to 300 mm.

A target inclination angle influences the film formation speed. In orderto obtain a high film formation speed, the target inclination angle isappropriate in a range of 0° to 45°, and a preferable target inclinationangle is in a range of 10° to 30°.

FIG. 9 shows upper and lower limits of T/S with which the phase angledistribution within ±2° and transmittance distribution within ±4° can berealized in the 152 mm square substrate with the change of the offsetdistance.

(3) The influence of the material of the light semi-transmission film onthe phase angle and transmittance will next be described in detail. Thephase angle and transmittance of the light semi-transmission film changewith the film formation speed and degree of nitriding. The filmformation speed and degree of nitriding are influenced by a nitrogenpartial pressure during sputtering. However, when the lightsemi-transmission film is completely nitrided, the influence of thenitrogen partial pressure during sputtering is reduced. In a nitridedmetal silicide film, a flow rate of nitrogen introduced duringsputtering is adjusted so that a content of nitrogen measured by ESCA islarger than that of silicon. This can reduce the influence of afluctuation of nitrogen partial pressure on the optical property. Withthis method, the distributions of the phase angle and transmittance inthe plane can also be reduced. Additionally, when oxygen is addedtogether with nitrogen during sputtering, the phase angle andtransmittance are largely influenced by a fluctuation of a flow rate ofoxygen. However, at least the influence of flow rate fluctuation ofnitrogen can be reduced in the aforementioned method.

Additionally, examples of the photo mask blank in the constitution ofthe present invention include a shield film (chromium, a chromiumcompound containing oxygen, nitrogen, carbon, and the like in chromium,another chromium compound, and the like) in the photo mask, the phaseshift film in the phase shift mask blank, and the like.

Moreover, the phase shift mask blank in the constitution of the presentinvention is not limited to the halftone phase shift mask blank. For apurpose of setting the dispersion of the phase angle within ±2°, thepresent invention can also be applied to the blank for manufacturingvarious types of the phase shift masks such as Levenson type, auxiliarypattern type, and self-matching type (edge emphasizing type).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of transfer principle of a halftone phaseshift mask.

FIG. 2 is a schematic view of a sputtering chamber in a DC magnetronsputtering apparatus used in an embodiment.

FIG. 3 is a graph showing dispersions of a phase angle and transmittanceamong blanks in the embodiment.

FIG. 4 is a graph showing dispersions of the phase angle andtransmittance among the blanks in another embodiment.

FIG. 5 is a graph showing a relation between DC power and phase angle.

FIG. 6 is a graph showing a relation of a film formation time with thephase angle and transmittance.

FIG. 7 is a graph showing a relation between a nitrogen flow rate andphase angle.

FIG. 8 is a schematic diagram showing a positional relation between atarget and a substrate.

FIG. 9 is a graph showing upper and lower limits of T/S with which aphase angle distribution within ±2° and a transmittance distributionwithin ±4° can be realized with a change of an offset distance.

FIG. 10 is a schematic diagram showing a sputtering apparatus of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples of the present invention will be described hereinafter infurther detail.

A DC magnetron sputtering apparatus described above with reference toFIG. 1 was used to continuously form films of 200 halftone phase shiftmask blanks for ArF excimer laser (193 nm) one by one at constantintervals.

Concretely, a mixed target (Mo:Si=8:92 mol %) of molybdenum (Mo) andsilicon (Si) was used to form a nitrided thin film (film thickness ofabout 670 angstroms) of molybdenum and silicon (MoSiN) on a transparentsubstrate by reactive sputtering (DC sputtering) in a mixed gasatmosphere (Ar:N₂=10%:90%, pressure: 0.1 Pa) of argon (Ar) and nitrogen(N₂). In this manner, the phase shift mask blank (film composition:Mo:Si:N=7:45:48) for ArF excimer laser (wavelength of 193 nm) wasobtained.

Here, a sputtering chamber 13 in the DC magnetron sputtering apparatusshown in FIG. 1 has a vacuum tank 1 as shown in FIG. 2. A magnetroncathode 2 and substrate holder 3 are disposed in the vacuum tank 1. Asputtering target 5 bonded to a backing plate 4 is attached to themagnetron cathode 2. In the example, oxygen-free steel is used in thebacking plate 4, and indium is used to bond the sputtering target 5 tothe backing plate 4. The backing plate 4 is directly or indirectlycooled by a water cooling mechanism. The magnetron cathode 2, backingplate 4 and sputtering target 5 are electrically connected to oneanother. A transparent substrate 6 is attached to the substrate holder3.

Additionally, in a constitution of the apparatus used in the presentexample, the sputtering target 5 and substrate 6 in FIG. 2 are arrangedso that opposite surfaces of the substrate and target form apredetermined angle as shown in FIG. 8. In this case, an offset distancebetween the sputtering target and the substrate was set to 340 mm, avertical distance between the target and the substrate (T/S) was 380 mm,and a target inclination angle was 15°.

The vacuum tank 1 is evacuated by a vacuum pump via an exhaust port 7.An atmosphere in the vacuum tank reaches a degree of vacuum which doesnot influence a property of the formed film, a mixed gas containingnitrogen is then introduced via a gas introduction port 8, a DC powersupply 9 is used to apply a negative voltage to the magnetron cathode 2,and sputtering is performed. The DC power supply 9 has an arc detectingfunction, and can monitor an electric discharge state during sputtering.A pressure inside the vacuum tank 1 is measured by a pressure gauge 10.

A transmittance of a light semi-transmission film formed on thetransparent substrate is adjusted by a type and mixture ratio of gasesintroduced via the gas introduction port 8. When the mixed gas containsargon and nitrogen, the transmittance is increased by increasing a ratioof nitrogen. When a desired transmittance cannot be obtained byadjusting the ratio of nitrogen, oxygen is added to the mixed gascontaining nitrogen, and the transmittance can further be increased.

A phase angle of the light semi-transmission film was adjusted by asputtering time, and the phase angle in an exposure wavelength wasadjusted to about 180°.

Evaluation of Dispersion among Blanks

Dispersions of the phase angle and transmittance among the blanks werechecked with respect to 200 phase shift mask blanks (size: 15.2 cmsquare) obtained as described above. Results are shown in FIG. 3.

As seen from FIG. 3, on and after the third blank, the halftone phaseshift mask blanks whose dispersions of the phase angle and transmittanceamong the blanks are within ±2° and within ±4°, respectively, cansteadily be manufactured. Additionally, it was confirmed also withrespect to the 11-th blank to 200-th blank that the dispersions of thephase angle and transmittance among the blanks were within ±2° andwithin ±4°, respectively. In this case, yield is 100% with respect tothe phase angle and transmittance.

Additionally, in Example 2, 200 blanks were prepared similarly as theaforementioned Example 1 except that the sputtering chamber was openedfor maintenance midway (at 190-th blank), and the dispersions of thephase angle and transmittance among the blanks were checked. Results areshown in FIG. 4.

As seen from FIG. 4, with use of the apparatus of the present invention,the halftone phase shift mask blanks whose dispersions of the phaseangle and transmittance among the blanks are within ±2° and within ±4°,respectively, can steadily be manufactured excluding first severalblanks and five blanks immediately after opening the sputtering chamber.It is also seen that the yield is 100% with respect to the phase angleand transmittance.

Moreover, a conventional manufacturing apparatus in which about tensubstrates were disposed in a load lock chamber, and an in-line typemanufacturing apparatus were used to manufacture the halftone phaseshift mask blanks. However, in either apparatus, it was difficult tosuppress the dispersions of the phase angle and transmittance among theblanks within ±2° and within ±4°, respectively, and the yield was bad.

Moreover, in Example 1, the transparent substrate was rotated duringfilm formation. Furthermore, the transparent substrate was rotatedinteger times from the start till the end of the film formation, whilethe film formation was performed. The dispersions of the phase angle andtransmittance in a plane were checked.

As a result, it was confirmed that the halftone phase shift mask blankshaving the dispersions of the phase angle and transmittance in the planewithin ±2° and ±4°, respectively, can steadily be manufactured.

Furthermore, the following was seen in the aforementioned examples.

As shown in FIG. 5, in order to suppress the dispersion of the phaseangle in a range of about 180° to about 172°, it is necessary to controla power of the DC power supply in a range of about 1.77 kW to about1.825 kW (preferably in a range of about 1.82 kW to 1.81 kW in order tosuppress the dispersion of the phase angle in a range of about 180° toabout 178°). Therefore, it is necessary to suppress a fluctuation of thepower of the DC power supply at a center value ±0.5%.

Similarly, as seen from FIG. 6, in order to suppress the dispersions ofthe phase angle and transmittance, it is necessary to control the filmformation time in a range of about 560 seconds to about 615 seconds(preferably about 600 seconds to about 594 seconds in order to suppressthe dispersion of the phase angle in a range of about 180° to about178°). Therefore, it is necessary to suppress a fluctuation of the filmformation time at a center value ±0.5%.

Similarly, as seen from FIG. 7, in order to suppress the dispersion ofthe phase angle, a flow rate of nitrogen introduced during sputtering isadjusted so that a content of nitrogen measured by ESCA in a nitridedmetal silicide film is larger than a content of silicon, and aninfluence of a fluctuation of nitrogen partial pressure on an opticalproperty is reduced. For this purpose, it is necessary to control theflow rate of nitrogen in a range of about 35 sccm or more (preferablyabout 35 sccm to about 35.5 sccm in order to suppress the dispersion ofthe phase angle in a range of about 180° to about 178°). Additionally,the nitrogen flow rate with which the influence of the fluctuation ofnitrogen partial pressure on the optical property can be reduced changeswith an exhaust property and DC power of the apparatus.

Evaluation of Dispersion in Plane

The dispersions of the phase angle and transmittance in a plane werechecked with respect to one of the phase shift mask blanks obtained asdescribed above.

As a result, the dispersion of the phase angle was within ±0.8° (averagevalue of 179.5°, range of 178.8° to 180.3°) in a range of 132 mm squareexcluding a substrate peripheral portion of 10 mm. Moreover, thedispersion of the transmittance was within ±1.3% (average value of6.16%, range of 6.08% to 6.23%).

Additionally, for comparison, when the film formation was performed atan offset distance of 340 mm, a vertical distance between the target andthe substrate (T/S) of 400 mm, and a target inclination angle of 15°,the dispersion of the phase angle was ±3.5° (average value of 178.8°,range of 175.3° to 181.7°). Moreover, the dispersion of thetransmittance was ±8% (average value of 6.07%, range of 5.83% to 6.56%).

Furthermore, for comparison, when the target was disposed opposite tothe substrate (offset distance of 0 mm, and target inclination angle of0°), the dispersion of the phase angle was ±2.7° (average value of179.8°, range of 177.1° to 182.0°) in a target diameter of 16 inchesφ.Moreover, the dispersion of the transmittance was ±4.2% (average valueof 6.19%, range of 6.00% to 6.45%).

With a larger offset distance, it is easier to reduce the dispersion inthe plane. However, when the offset distance is excessively large, acapacity of the vacuum tank increases, evacuation property is thereforedeteriorated, and further a film formation speed is lowered.

Additionally, the dispersion in the plane was evaluated by judgingwhether or not both a maximum point (plus value) and minimum point(minus value) with respect to the average value (center value) werewithin a defined range.

The preferred examples of the present invention have been describedabove, but the present invention is not limited to the aforementionedexamples.

For example, molybdenum was used as a metal constituting the lightsemi-transmission film, but this is not limited, and zirconium,titanium, vanadium, niobium, tantalum, tungsten, nickel, palladium, andthe like can be used.

Moreover, the target of molybdenum and silicon was used as the targetcontaining metal and silicon, but this is not limited. In the targetcontaining metal and silicon, molybdenum is particularly superior amongthe aforementioned metals in controllability of the transmittance and inthat a target density increases and particles in the film can be reducedwith use of the sputtering target containing metal and silicon.Titanium, vanadium, and niobium are superior in resistance to analkaline solution, but slightly inferior to molybdenum in the targetdensity. Tantalum is superior in the resistance to the alkaline solutionand target density, but slightly inferior to molybdenum in thecontrollability of transmittance. Tungsten has properties similar tothose of molybdenum, but is slightly inferior to molybdenum in anelectric discharge property during sputtering. Nickel and palladium aresuperior in the optical property and resistance to the alkalinesolution, but dry etching is slightly difficult to perform. Zirconium issuperior in the resistance to the alkaline solution, but inferior tomolybdenum in the target density, and the dry etching is slightlydifficult to perform. Considering these, molybdenum is most preferableat present. Molybdenum is also preferable for a nitrided molybdenum andsilicon (MoSiN) thin film (light semi-transmission film) in superiorchemicals resistance such as acid resistance and alkali resistance.

Moreover, in order to obtain the thin film of a composition in whichelectric discharge stability is secured during film formation andvarious properties of the phase shift mask are satisfied, the targetcontaining 70 to 95 mol % of silicon, and metal is preferably subjectedto DC magnetron sputtering in the atmosphere containing nitrogen.Thereby, the light semi-transmission film containing nitrogen, metal andsilicon is preferably formed.

When the content of silicon in the target is larger than 95 mol %, avoltage is not easily applied (electricity is not easily passed) to atarget surface (erosion portion) in the DC sputtering, and the electricdischarge becomes unstable. Moreover, when the content of silicon isless than 70 mol %, the film constituting a light semi-transmissionportion with a high transmittance cannot be obtained. Furthermore,electric discharge stability is further enhanced by combination of thenitrogen gas with the DC sputtering.

Additionally, the electric discharge stability during film formationalso influences film quality. When the electric discharge stability issuperior, the light semi-transmission film with a satisfactory filmquality is obtained.

As described above, according to the present invention, there can beprovided the manufacturing method of the phase shift mask blank in whichthe dispersions of phase angle and transmittance among blanks can bereduced as much as possible and the yield is satisfactory.

Moreover, there can be provided the manufacturing method of the phaseshift mask blank in which the dispersions of phase angle andtransmittance in the plane of the blanks can be reduced as much aspossible and the yield is satisfactory.

Furthermore, there can be provided the manufacturing apparatus of thephase shift mask blank in which the dispersions of phase angle andtransmittance among the blanks can be reduced as much as possible andwhich can be manufactured with the satisfactory yield.

Additionally, there can be provided the manufacturing apparatus of thephase shift mask blank in which the dispersions of phase angle andtransmittance in the plane of the blanks can be reduced as much aspossible and which can be manufactured with the satisfactory yield.

What is claimed is:
 1. A method of continuously manufacturing aplurality of phase shift mask blanks each having at least a phase shiftfilm on a transparent substrate, said method comprising a step of: usinga sputtering method to continuously form the phase shift film on thetransparent substrate, wherein a dispersion of a phase angle of thephase shift film among said plurality of blanks is within ±2°.
 2. Amethod of continuously manufacturing a plurality of halftone phase shiftmask blanks each having a light semi-transmission film on a transparentsubstrate, said method comprising a step of: using a sputtering methodto continuously form the light semi-transmission film on the transparentsubstrate, wherein dispersions of a phase angle and a transmittance ofthe light semi-transmission film among said plurality of halftone phaseshift mask blanks are within ±2° and within ±4%, respectively.
 3. Amethod of continuously manufacturing a plurality of photo mask blankseach having at least a thin film for forming a pattern on a transparentsubstrate, said method comprising a step of: using a sputtering methodto continuously form said thin film on said transparent substrate,wherein said step of using the sputtering method to continuously formsaid thin film on said transparent substrate comprises steps of:successively subjecting a plurality of substrates to a series ofprocesses of supplying the transparent substrate into a sputteringchamber, forming the thin film for forming the pattern in saidsputtering chamber, and discharging the transparent substrate with thefilm formed thereon from said sputtering chamber; and supplying anddischarging the transparent substrate at a constant interval in order toset a film formation time to be constant among the plurality of blanks,and at least first to fifth photo mask blanks after start of filmformation are excluded from the photo mask blanks obtained in said step.4. The manufacturing method according to claim 3 wherein said thin filmfor forming the pattern is a phase shift film, and said photo mask blankis a phase shift mask blank.
 5. The manufacturing method according toclaim 3 wherein said thin film for forming the pattern is a lightsemi-transmission phase shift film, and said photo mask blank is ahalftone phase shift mask blank.